plants Review Cabbage Production in West Africa and IPM with a Focus on Plant-Based Extracts and a Complementary Worldwide Vision Abla Déla Mondédji 1,2,*, Pierre Silvie 2,3,4 , Wolali Seth Nyamador 1, Pierre Martin 2,4 , Lakpo Koku Agboyi 5, Komina Amévoin 1, Guillaume Koffivi Ketoh 1 and Isabelle Adolé Glitho 1 1 Laboratoire d’Ecologie et d’Ecotoxicologie, Faculté des Sciences, Université de Lomé, Lomé 1 01B.P. 1515, Togo; [email protected] (W.S.N.); [email protected] (K.A.); [email protected] (G.K.K.); [email protected] (I.A.G.) 2 CIRAD, Agroécologie et Intensification Durable Des Cultures Annuelles (AIDA), 34398 Montpellier, France; [email protected] (P.S.); [email protected] (P.M.) 3 Institut de Recherche Pour le Développement, UMR IPME, 34AA001 Montpellier, France 4 AIDA, CIRAD, Montpellier University, CEDEX 05, 34398 Montpellier, France 5 CABI West Africa, PO Box CT 8630, Cantonments, Accra GA 0376800, Ghana; [email protected] * Correspondence: [email protected]; Tel.: +228-90109317 Abstract: In urban and peri-urban areas in West Africa, the cabbage Brassica oleracea L. (Brassicaceae) is protected using repeated high doses of synthetic insecticides. After a brief description of available IPM components, this paper presents a literature review focused on the botanical extracts that have been experimented with at the laboratory or in the field in West Africa against major cabbage pests. The literature reviewed mentions 19 plant species from 12 families used for cabbage protection in the subregion. The species most used are Azadirachta indica, Capsicum frutescens, Ocimum gratissimum Citation: Mondédji, A.D.; Silvie, P.; and Ricinus communis. An overview of the world literature showed that a total of 13 plant species Nyamador, W.S.; Martin, P.; Agboyi, belonging to 8 families used to control cabbage pests are reported from the rest of Africa, and L.K.; Amévoin, K.; Ketoh, G.K.; 140 plant species belonging to 43 families from the rest of the world. The most commonly used and Glitho, I.A. Cabbage Production in tested plant species against insect pests in the three geographical areas considered is A. indica. West Africa and IPM with a Focus on Plant-Based Extracts and a Keywords: Plutella xylostella; Hellula undalis; Lipaphis erysimi; Brevicoryne brassicae; Lipaphis pseudobras- Complementary Worldwide Vision. sicae; pesticidal plants Plants 2021, 10, 529. https:// doi.org/10.3390/plants10030529 Academic Editor: Kirstin Wurms 1. Introduction Received: 28 December 2020 In Africa, where vegetables are gaining ground in people’s diets, vegetable production Accepted: 26 February 2021 is taking on more importance in the socioeconomic sector and sown areas are expanding. Published: 11 March 2021 Nutritionally, vegetables improve the basic diet of populations [1], while economically and socially, their production significantly reduces unemployment [2] by giving job opportuni- Publisher’s Note: MDPI stays neutral ties to a significant segment of urban dwellers [3]. with regard to jurisdictional claims in Urban demand for fresh vegetables is steadily increasing [4,5]. The development of published maps and institutional affil- vegetable growing in urban and peri-urban areas has the advantage of bringing farmers iations. closer to consumers while making the most efficient use of agricultural water infrastruc- tures. In urban and peri-urban areas of Africa, vegetables are often produced on small plots. Market gardening mostly concerns the production of vegetables. The main vegetable crops grown in the countries of the Economic Community of Western African States Copyright: © 2021 by the authors. (ECOWAS) are lettuce (Lactuca sativa L.), tomato (Solanum lycospersicum L.), cabbages (Bras- Licensee MDPI, Basel, Switzerland. sica oleracea L.), carrot (Daucus carota L.), African eggplant (Solanum macrocarpon L.), onion This article is an open access article (Allium ascalonicum L., Allium cepa L.), bean (Phaseolus vulgaris L.), cucumber (Cucumis distributed under the terms and sativus L.), eggplant (Solanum melongena L.), beetroot (Beta vulgaris L.), okra (Abelmoschus conditions of the Creative Commons esculentus (L.) Moench), purple amaranth (Amaranthus blitum L.) and jute mallow or ‘crin- Attribution (CC BY) license (https:// crin’ (Corchorus olitorius L.) [6,7]. Phytosanitary constraints are burdensome in the tropics, creativecommons.org/licenses/by/ where conditions are favourable for the development and proliferation of many crop pests 4.0/). Plants 2021, 10, 529. https://doi.org/10.3390/plants10030529 https://www.mdpi.com/journal/plants Plants 2021, 10, 529 2 of 36 (insects, mites, nematodes, pathogens, etc.). In addition to the quantitative losses that could be easily assessed, there are qualitative ones related to market demand and customer perception. A damaged cabbage plant, for example, represents a loss of one kilogram of cabbage head, i.e., a mean financial loss of 300 ± 100 F CFA (0.6 ± 0.2 USD) [8]. Whole- salers, who are important middlemen in the distribution chain, usually purchase entire vegetable beds, unless elements of the bed display visible blemishes, in which case these will be excluded to avoid putting off the consumer who is focused on the appearance of vegetables [9]. Therefore, farmers rely on cheap and effective pest control methods. Chemical pest control, using synthetic pesticides, is one such method [10–12] and is still the most used by vegetable farmers throughout the world [13,14]. However, this crop pest management method has serious environmental drawbacks [15,16] because it results in adverse effects on useful species [17] and exposes humans and animals to serious poi- soning [18–22]. Uncontrolled use of synthetic pesticides leads also to the development of pesticide resistance in populations of pests and pathogenic agents [23,24]. The concept of Integrated Pest Management (IPM) [25,26] nonetheless emerged more than 60 years ago and developed into a number of components such as biological pest control [27–29], pest-resistant cultivars [30–32], physical control and farming practices such as protection nets [33,34], crop diversification and companion planting [35,36], and the use of plant extracts [37–40]. The general aim of this paper is to review the situation of the protection of the round- headed cabbage B. oleracea L. var. capitata (Brassicacae), which is the most widely cultivated cabbage in Western Africa (ECOWAS zone) and one of the most important vegetable crops. This species is one of the main exotic leaf vegetables [41,42]. It is available all year round and commonly used in various West African recipes, in homes and restaurants alike, in particular during festivities. The substantial parasitic pressure exerted by insects and pathogens incites cabbage-farmers to make liberal use of synthetic pesticides [22,43]. This paper begins by presenting the main characteristics of the cabbage production system, showing the different elements of the context. It then lists the constraints to be dealt with, including those related to insect pests, and goes on to describe the various pest-control methods used. Brief description is given on chemical control methods using synthetic substances as well as the perception of farmers who use them and on the risks induced. Rules and regulations currently in force are summarised. The paper thereafter dwells more extensively on the diverse uses of plant extracts under trial or adopted in West Africa and presents a global review of literature on the subject. 2. Materials and Methods The literature review was conducted using two main approaches. The Web of Science (WoS) database was searched with the available options (all databases between 1900 and April 2020), using as associated search words the scientific names of the main known pest species (‘Bemisia tabaci’, ‘Brevicoryne brassicae’, ’Chrysodeixis chalcites’, ‘Crocidolomia binotalis’, ‘Helicoverpa armigera’, ‘Heliothis armigera’, ‘Hellula undalis’, ‘Lipaphis erysimi’, ‘Myzus persicae’, ‘Plutella xylostella’, ‘Trichoplusia ni’) and the terms ‘plant extract’, ‘botanical’ and ‘cabbage’. Since the WoS database does not include all the existing references, this first collection was completed with information found in papers, dissertations, technical information sheets and reports found via African references extracted from Google, Google Scholar, CIRAD’s Agritrop database and the Knowledge Base Knomana (KNOwledge MANAge- ment on pesticide plants in Africa) database currently being composed. Articles obtained from the WoS database were compiled in a Zotero library. Documents concerning the production systems, constraints faced, various control methods and existing rules and reg- ulations were sought after in the published literature, but above all in reports, Master’s and PhD dissertations and technical datasheets, all detailed in the bibliographical references. Plants 2021, 10, 529 3 of 36 3. Results 3.1. Cabbage Production Systems in Urban and Peri-Urban Areas of West Africa 3.1.1. Social and Demographic Characteristics of Cabbage Farmers Social and demographic data on cabbage farmers were obtained through results of surveys on vegetable farmers in different countries of West African subregion. The ages of the farmers interviewed ranged between 15 to 80 years [44,45], with 20–50 years dominant. The proportion of women varies from sample to sample: 31.6% in Benin [46], 22.0% in Côte d’Ivoire [47], 30.9% in Ghana [46], 0% in Niger [7], 27.0% in Nigeria [45], 28.0% in Togo [44]. On average, the farmers